Last month, we tested readers on commissioning three of the many automatic temperature control (ATC) sequences of operation associated with the secondary hot water process heating system for an industrial building application. This month’s Back2Basics is to water balance this existing system and to test readers on water balancing the primary — secondary water system at maximum design water flow during the heating season. Not included in this test are the following TAB requirements:
- Water balance building side during the fall and spring seasons for heating design water flow by the process heating pump.
- Water balance building side during the summer for heating design flow by the process heating.
The energy retrocommissioning team continues to include the facility manager, process engineering manager, ATC operator, commissioning engineer, TAB engineer, and if possible, a LEED Accredited Professional. Going forward, the team, and more specifically the facility manager, will continue to be responsible for collecting the incoming utility bills and measure them to the past utility bills to compare the difference in energy usage, as well as to maintain good boiler log operating data.
We discussed in the October B2B test the two ways to approach energy retrocommissioning opportunities, which are:
- Installation of devices to monitor the system and its associated process equipment over an agreed-upon period, review the data collected, and assess whether to proceed with the energy conservation initiative.
- Complete an initial cursory review of the original design intent versus actual operating conditions, and assess whether to proceed with the energy conservation initiative.
- Equally important is the documenting of the Basis of Design (BofD) for the original HVAC design and the future HVAC design (once the energy retrocommissioning solution plan is mutually agreed upon).
To complete this month’s TAB tasks, the TAB engineer shall complete the following:
- Document the existing secondary hot water process heating system pump performance so as to be able to benchmark and document water balancing improvements when comparing the existing systems to the new, energy retrocommissioning results.
- Document the existing water pump data to contribute energy conservation calculations to justify the replacement of the secondary pump for more optimum pump curve selection and its associated, smaller high-efficiency motors. These changes will have been identified in the original ECM assessment and would take into account the changing out of pump motors, motor starter sizes, etc., based on pump curve performance and reduction in water system total pump head and GPM.
- Create system flow diagrams for the retrocommissioned secondary hot water pumping system incorporating pertinent operating data (piping pressure drop from pump discharge back to the pump inlet, pipe velocity, pressure drops through equipment, etc.).
Before the TAB engineer can complete the flow diagram, she must also review the existing Basis of Design document to clearly understand how the system was/is to work. It is important to note that the TAB engineer may complete the water flow readings in sync with the commissioning engineer completing his ATC/FPT pass-fail documentation (see last month’s B2B for example).
The TAB engineer should review record drawings, existing equipment shop drawings, and if necessary, make a “best guess” as to the original design calculations (i.e., pressure drop across the strainer) based on her experience with water system pressure drops. This information is inputted into the TAB System Flow Diagram TAB-3 process to document the estimated “Design” pressure drop readings. Next, the TAB engineer picks up the tools and completes the water system readings, documenting the “actual” flow, pressure drop, and velocity, and note this data on the Design-to-Actual TAB flow diagram. Now the auditors have Design-to-Actual data to analyze.
This month’s test is for you to select the correct answers in each of the remarks column next to each water pressure drop reading. Refer to the B2B page 2, TAB System Flow diagram, and note Design-To-Actual findings. The answers can be found at www.esmagazine.com.
When coordinating the ATC/FPT-TAB initiative, the energy retrocommissioning team should use an Equipment Assessment Checklist to complete a static condition assessment of the equipment/system and to also identify energy retrocommissioning opportunities. See the Facility Files column for sample Equipment Assessment Checklist for the primary and secondary pump installations. Any deficiencies identified via the checklists need to be added to the Corrective Action Log, too. It is also important that auditors avoid assuming that there were no previous installation problems that were never identified prior to the building owner accepting this primary-secondary pumping system installation. These deficiencies may be an integral part of the energy retrocommissioning issues and concerns and may have compromised system performance and energy wasted in the past.
With Data Analysis Phase and Solution Planning Phase completed, the energy retrocommissioning team can reformat the Corrective Action Log into a “Matrix of Opportunity” or Energy Conservation Measure (ECM) Report for presentation to those funding the energy retrocommissioning project. This will lead to the Solution Implementation Phase. An example of ROI parameters established for this B2B series are the following ECM Implementation Levels:
Level 1 = Quick-Fix (no cost or low cost) ROI
Level 2 = 1-year to 2-year ROI
Level 3 = 2+ years to 4-year ROI
Level 4 = 4+ years to 6-year ROI